The present invention relates to a method of and an apparatus for actuating an operation.
In the field known as “sentient computing”, a system for locating each of a plurality of transponders is disclosed in GB 2 320 089, GB 2 332 052, GB 2 332 053, GB 2 332 054, GB 2 332 055, and British Patent Application No. 9929900.0. Each transponder comprises a receiver for receiving a radio signal directed to all of the transponders of the system. The output of the receiver is connected to a decoder for recognising the code corresponding to the individual transponder. When that code is received, the decoder actuates an ultrasonic transducer, which emits a short burst or single pulse of ultrasonic radiation. The transponder also comprises a transmitter which can be manually actuated by a switch to transmit a radio signal carrying the code of the individual transponder.
A plurality of ultrasonic transducers are distributed spatially about an environment in which the transponders are to be located. For example, the environment may comprise a single room or a set of rooms constituting an office, laboratory or other commercial establishment. The receiving transducers are, for example, disposed on the ceilings of the room or rooms and convert received ultrasonic pulses into corresponding electrical pulses which are supplied to a central processing unit.
The central processing unit is connected to a transmitter which transmits the transponder codes in sequence so as to poll the transponders in turn. In particular, each transponder code is used to modulate a radio frequency carrier and the codes are transmitted in sequence with sufficiently large gaps between consecutive codes for the ultrasonic energy transmitted by each transponder to have decayed sufficiently before the next transponder is polled so as to avoid confusion. The time delay between polling each transponder and the initial time of arrival of the ultrasonic pulse which it emits to each receiving transducer allows the central processing unit to determine the position of each transponder to within a few centimeters of its actual location.
The central processing unit is also connected to a receiver which receives the signals transmitted by the transponders and actuates predefined operations in response thereto.
JP 11167688 A discloses an arrangement which is concerned with the management of the elderly and infirm so as to prevent their wandering out of or escaping from an institution providing residential care. The inmates wear shoes containing a form of transponder which is actuated upon receipt of induced power so as to transmit a code identifying the inmate. Access points in various boundaries are provided with sensors which power a transponder by induction when the transponder is crossing a boundary and which receive the code identifying the inmate and forward it via a hard-wired network to a central control together with a code identifying the location at the boundary. The sensors are generally fixed at doorways and gateways and the system can only infer, from detection of boundary crossings, whether each inmate is inside or outside a room, building or the like. Such a system cannot therefore detect the position of an inmate anywhere within the area which is covered by the system but can, at best, only give an indication of whether an inmate is within a given boundary or between two nested boundaries. The positions of the sensors are fixed and predetermined in such a way that they cannot be arbitrarily selected. Further, the locations of the sensors are associated with the crossing of one or more boundaries by inmates.